How to determine username and password in java

How does Java determine the username and password? Java verification username and password

Assume that a username and password need to be entered in the login interface of a warehouse management system. The username can only consist of 6~10 digits, and the password can only have 6 digits. Any failure to meet the username or password requirements is considered an exception and needs to be caught and handled.

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The following uses a custom exception class to complete the verification function of user login information. The implementation steps are as follows.

(1) Write a custom exception class LoginException, which inherits from Exception. The LoginException class contains two constructors, namely the constructor without parameters and the constructor with one parameter. The code is as follows:

public class LoginException extends Exception
{
public LoginException()
{
super();
}
public LoginException(String msg)
{
super(msg);
}
}

(2) Create the test class Test08, in The validateLogin() method is defined in this class to verify username and password. When the username or password does not meet the requirements, use the custom exception class LoginException to output the corresponding exception information. The validateLogin() method is defined as follows:

public boolean validateLogin(String username,String pwd)
{
boolean con=false; //用户名和密码是否正确
boolean conUname=false; //用户名格式是否正确
try
{
if(username.length()>=6&&username.length()<=10)
{
for(int i=0;i<username.length();i++)
{
char ch=username.charAt(i); //获取每一个字符
if(ch>=&#39;0&#39;&&ch<=&#39;9&#39;)
{ //判断字符是否为0~9的数字
conUname=true; //设置 conUname 变量值为 true
}
else
{ //如果字符不是0~9的数字，则拋出LoginException异常
conUname=false;
throw new LoginException("用户名中包含有非数字的字符！");
}
}
}
else
{ //如果用户名长度不在6~10位之间，拋出异常
throw new LoginException("用户名长度必须在6〜10位之间！");
}
if(conUname)
{ //如果用户名格式正确，判断密码长度
if(pwd.length()==6)
{ //如果密码长度等于6
con=true; //设置con变量的值为true，表示登录信息符合要求
}
else
{ //如果密码长度不等于6，拋出异常
con=false;
throw new LoginException("密码长度必须为 6 位！");
}
}
}
catch(LoginException e)
{ //捕获 LoginException 异常
System.out.println(e.getMessage());
}
return con;
}
(3) 在 Test08 类中添加 main() 方法，调用 validateLogin() 方法，如果该方法返回 true，则输出登录成功的信息。main() 方法的定义如下：
 
public static void main(String[] args)
{
Scanner input=new Scanner(System.in);
System.out.println("用户名：");
String username=input.next();
System.out.println("密码：");
String password=input.next();
Test08 lt=new Test08 ();
boolean con=lt.validateLogin(username,password); //调用 validateLoginO 方法
if(con)
{
System.out.println("登录成功！");
}
}

In the validateLogin() method of this program, conditional control statements and for loop statements are used to verify the user name and password respectively. Any situation that does not meet the username or password requirements will throw a custom exception LoginException, catch the exception in the catch statement, and output the exception information.

Run the program. When the user name entered by the user contains non-numeric characters, a LoginException exception will be thrown. Execute the code in the catch statement block to print the exception information, as shown below.

用户名：
xiake8!
密码：
123456
用户名中包含有非数字的字符！

When the user name entered by the user is not longer than 6~10 characters, a LoginException exception will also be thrown and the exception information will be printed, as shown below.

用户名：
administrator
密码：
123456
用户名长度必须在6~10位之间！

When the login password entered by the user is not equal to 6 digits, a LogWException exception will also be thrown and the exception information will be printed, as shown below.

用户名：
20181024
密码：
12345
密码长度必须为 6 位！

When the user name and password entered by the user meet the requirements, the login successful information will be printed, as shown below.

用户名：
20181024
密码：
123456
登录成功！

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